Food Waste at Record High: How Vacuum Technologies Help Reduce Waste
According to a report by the Food and Agriculture Organization of the United Nations, at least a third of food is lost or wasted between harvest and home. In North America and Europe, this means more than 100 kg of food lost per capita, amounting to 1.3 billion tonnes annually worldwide. A reduction in this huge mass of food produced in vain would go a long way towards reducing the greenhouse effect.
How can vacuum technology help reduce food waste and improve packaging?
1. Vacuum packaging helps keep food longer.
Because vacuum food packaging removes air from the package prior to sealing, the longevity or 'shelf life' of food can be significantly improved. For example, at pressures close to 1 mbar, almost all oxygen is removed. This drastically reduces the growth of bacteria and fungi as they need oxygen to grow and allows food to last much longer. With vacuum packaging, the shelf life for canned meat is between 2 and 4 weeks, while for pork or sausages it is up to 10 days.
In vacuum food packaging, evacuation (the process by which air is removed from a container) is usually done by single stage rotary vane pumps or dry screw pumps. The advantage of dry screw pumps in this application is their long maintenance intervals and therefore a longer uptime of the packaging machines.
Furthermore, quality assurance is an important issue for the food industry. The tightness of a container must be guaranteed to preserve quality (and therefore shelf life), as well as to prevent the entry of bacteria or spores.
To keep bacteria and spores away, the tightness must be <10-5 Pa · m 3 / s.
2. Vacuum cooling helps keep fruits and vegetables fresh.
Vegetables, salads and flowers can be cooled very efficiently in a vacuum, and directly after harvest, if necessary. Rapid vacuum cooling means that complete food containers can be evacuated at pressures of> 6 mbar. Below 23 mbar, the food begins to cool. With vacuum food packaging technology, an entire container can be cooled and ready for shipment in less than 30 minutes.
This rapid cooling is achieved thanks to the phase diagram of the water. At 20 ° C, the water vapor pressure is 23 mbar. When reduced to 8 mbar, the water in the fruit or lettuce has to reduce its temperature to 5 ° C. On the contrary, the loss of water content is negligible and the products remain fresh. Evacuation at pressures below the triple point of water (6 mbar) should be avoided as the food would freeze and the cell structure could be damaged.
Vacuum technology rapidly cools food products from their core, providing a much longer shelf life by immediately slowing the growth of bacteria. This method requires very little energy and investment, and can even be done in remote areas where there is no fresh water.
Typically the vacuum pumps used are medium size single stage rotary vane pumps with pumping speeds up to 300 m³ / h (often with root top pumps) or dry screw pumps due to their high tolerance to water vapor.
3. Vacuum drying helps keep meats and fish fresh
Fresh food products spoil quickly unless some way is found to preserve them. Since ancient times, foods such as fish or sausages have been dried in the sun and in the open air. This is because bacteria need water to grow.
There are 2 different processes for drying food with the support of vacuum:
Microwave Vacuum Drying ('VMD') and Freeze Drying ('FD', 'Freeze Drying')
In VMD, the products are heated by microwave to 35-60 ° C while the vacuum pump maintains the pressure around 10 mbar. Then the water content evaporates. In FD, the products are cooled to -20-40C and the water sublimates at pressures below 0.1 and -1 mbar of the solid phase.
This process is also used to freeze-dry coffee, pharmaceuticals, and preserve historical books in libraries.
The vacuum pumps used are single stage (VMD) or two stage (FD) rotary vane pumps, combined with water condensers and open gas ballast pumps or dry screw pumps. Dry pumps have the advantage that they can handle the water vapor from the drying process, so the condenser is unnecessary.
These few examples show the diversity of vacuum applications in food processing and how vacuum technologies help reduce waste and contribute to our environment.
Source: Vacuum Science World